1. Field of the Invention
The invention relates to a double drum filter, particularly vacuum filter with oppositely rotating drums for the filtration of suspensions containing solids.
2. Description of the Prior Art
In the field of filter technique, there is described in the German Laid Open No. 2,322,155 a double drum filter for the dehydration of fibrous constituents in a suspension, for example, paper pulp, in which two rotatably positioned and oppositely driven drums are arranged with parallel axes in a closed pressure tank and form between them a roller gap or clearance. The drum-shaped filters in this connection assume both the function of the dehydration of the paper pulp as well as also the transportation of the dehydrated fibrous and conherent filter cake. The drums with parallel axes arranged adjacent one another act in this connection as in the case of a stand of rolls. The material rising high from the roller gap and dehydrated, reaches a removal apparatus arranged vertically above the roller gap. Filters of this type of construction are, however, not adapted for the filtration of suspensions containing finely granular solid substances, such as coal sludge, flotation concentrates, etc.
For the filtration of suspensions containing solid substances with double drum filters it is on the other hand suggested to carry out the filter charge from above in the center between both filter drums and to bridge over the roller gap with a stationary trough-floor or -bottom which is arranged on the drum-stand. For the sealing of the trough with respect to the rotating drums, expensive sealing elements, such as gummed sealing strips had to be provided. The sealing on the filter surface by means of sealing strips has the disadvantage, that the sealing strips, on the one hand, are subject to a high wear, and on the other hand, cause a high wear of the filter-tissue.
Such a type of construction, after brief time in operation, leads to a high amount of dripping water, so that the filter must be put out of operation. For the filtration of finely granular, wearing solid substances in a suspension, such as flotation concentrates or coal sludges these filters are not adapted and were for the above reasons not engaged in.